This thesis studies the application of Si based nanowires produced from metal assisted chemical etching (MACE) for the detection of biomolecules. The fabrication of high aspect ratio dense nanowire was achieved through gold catalysed etching on silicon. Glancing Angle Deposition (GLAD) was used to form catalyse nano-clusters. The resulting material was characterized by novel methods such as thermoporometry. Oligonucleotide DNA was grafted to the nanowire surface to produce a high capacity substrate with high sensitivity, large dynamic range as well as low steric hindrance. On the hydrophilic nanowires. We have shown that miniaturized high quality detection site can be achieved with photo-induced attachment. Lastly, DNA Direct Addressing (DDA) was used for the production of a protein detection platform on nanowire substrate. A proof-of-concept platform was shown to be capable of cytokine detection in human serum. The thesis shows that the substrate could be a versatile platform for bio-analytes detection.